1. Field of the Invention
The present invention relates to a vehicular transmission including a main shaft, a countershaft, gear trains of a plurality of gear positions, a shift drum, a shift drum center, a drum stopper arm, and an intermittent feed mechanism. Specifically, the main shaft can receive power transmitted from an engine. The countershaft is connected to a drive wheel. The gear trains of the plurality of gear positions are disposed between the main shaft and the countershaft, allowing the plurality of gear positions to be selectively established. The shift drum has a lead groove formed on an outer periphery thereof for selecting an established state of the gear trains of the plurality of gear positions. The shift drum center rotates with the shift drum. The drum stopper arm engages in an outer periphery of the shift drum center and is urged toward a center of rotation of the shift drum center in order to determine a position of rotation of the shift drum center. The intermittent feed mechanism rotatably drives the shift drum center intermittently. The transmission shuts down power transmission from the engine to the main shaft when the established state of the gear trains is selected.
2. Description of Background Art
A known vehicular transmission, as disclosed, for example, in Japanese Patent Laid-open No. Sho 59-106014, selects the established state of the gear trains of a plurality of gear positions by rotatably driving intermittently a shift drum center that rotates with a shift drum.
The vehicular transmission disclosed in Japanese Patent Laid-open No. Sho 59-106014 includes notches disposed on an outer periphery of the shift drum center. The notches are equally spaced apart from each other in a circumferential direction of the shift drum center, each corresponding individually to each of the plurality of gear positions. An intermittent feed mechanism included in this transmission rotatably drives the shift drum center intermittently by only an angle corresponding to the distance between two adjacent notches. Consequently, when the established state of the gear trains of the plurality of gear positions is selected, a large engagement noise results because of a relatively large difference in speed between the shifter and a gear to be engaged with the shifter. This is particularly conspicuous in a vehicle arranged to select automatically a gear position according to an upshift or downshift operation and arranged to make a preliminary gearshift during running at a given gear position. Specifically, in such a vehicle, there is produced a large engagement noise that is not operatively associated with an operation performed by an occupant of the vehicle. This gives the occupant a sense of discomfort.
The present invention has been made to address the foregoing situation and it is an object of the present invention to provide a vehicular transmission that can suppress the engagement noise produced when the shifter is moved slidably to select a gear position.